CD22 blockade aggravates EAE and its role in microglia polarization.

AIMS: Multiple sclerosis (MS) is a neuroinflammatory demyelinating disease. Microglia are reportedly involved in the pathogenesis of MS. However, the key molecules that control the inflammatory activity of microglia in MS have not been identified. METHODS: Experimental autoimmune encephalomyelitis (EAE) mice were randomized into CD22 blockade and control groups. The expression levels of microglial CD22 were measured by flow cytometry, qRT-PCR, and immunofluorescence. The effects of CD22 blockade were examined via in vitro and in vivo studies. RESULTS: We detected increased expression of microglial CD22 in EAE mice. In addition, an in vitro study revealed that lipopolysaccharide upregulated the expression of CD22 in microglia and that CD22 blockade modulated microglial polarization. Moreover, an in vivo study demonstrated that CD22 blockade aggravated EAE in mice and promoted microglial M1 polarization. CONCLUSION: Collectively, our study indicates that CD22 may be protective against EAE and may play a critical role in the maintenance of immune homeostasis in EAE mice.

Oxidative phosphorylation regulates B cell effector cytokines and promotes inflammation in multiple sclerosis.

Dysregulated B cell cytokine production contributes to pathogenesis of immune-mediated diseases including multiple sclerosis (MS); however, the underlying mechanisms are poorly understood. In this study we investigated how cytokine secretion by pro-inflammatory (GM-CSF-expressing) and anti-inflammatory (IL-10-expressing) B cells is regulated. Pro-inflammatory human B cells required increased oxidative phosphorylation (OXPHOS) compared with anti-inflammatory B cells. OXPHOS reciprocally modulated pro- and anti-inflammatory B cell cytokines through regulation of adenosine triphosphate (ATP) signaling. Partial inhibition of OXPHOS or ATP-signaling including with BTK inhibition resulted in an anti-inflammatory B cell cytokine shift, reversed the B cell cytokine imbalance in patients with MS, and ameliorated neuroinflammation in a myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalitis mouse model. Our study identifies how pro- and anti-inflammatory cytokines are metabolically regulated in B cells and identifies ATP and its metabolites as a "fourth signal" that shapes B cell responses and is a potential target for restoring the B cell cytokine balance in autoimmune diseases.

A TH17-intrinsic IL-1ß-STAT5 axis drives steroid resistance in autoimmune neuroinflammation.

Steroid resistance poses a major challenge for the management of autoimmune neuroinflammation. T helper 17 (TH17) cells are widely implicated in the pathology of steroid resistance; however, the underlying mechanisms are unknown. In this study, we identified that interleukin-1 receptor (IL-1R) blockade rendered experimental autoimmune encephalomyelitis (EAE) mice sensitive to dexamethasone (Dex) treatment. Interleukin-1ß (IL-1ß) induced a signal transducer and activator of transcription 5 (STAT5)-mediated steroid-resistant transcriptional program in TH17 cells, which promoted inflammatory cytokine production and suppressed Dex-induced anti-inflammatory genes. TH17-specific deletion of STAT5 ablated the IL-1ß-induced steroid-resistant transcriptional program and rendered EAE mice sensitive to Dex treatment. IL-1ß synergized with Dex to promote the STAT5-dependent expression of CD69 and the development of central nervous system (CNS)-resident CD69+ TH17 cells. Combined IL-1R blockade and Dex treatment ablated CNS-resident TH17 cells, reduced EAE severity, and prevented relapse. CD69+ tissue-resident TH17 cells were also detected in brain lesions of patients with multiple sclerosis. These findings (i) demonstrate that IL-1ß-STAT5 signaling in TH17 cells mediates steroid resistance and (ii) identify a therapeutic strategy for reversing steroid resistance in TH17-mediated CNS autoimmunity.

[Immune Regulation by TNF Receptor-associated Factor 5].

The tumor necrosis factor receptor (TNFR)-associated factor (TRAF) family of molecules are intracellular adaptors that regulate cellular signaling through members of the TNFR and Toll-like receptor superfamily. Mammals have seven TRAF molecules numbered sequentially from TRAF1 to TRAF7. Although TRAF5 was identified as a potential regulator of TNFR superfamily members, the in vivo function of TRAF5 has not yet been fully elucidated. We identified an unconventional role of TRAF5 in interleukin-6 (IL-6) receptor signaling involving CD4+ T cells. Moreover, TRAF5 binds to the signal-transducing glycoprotein 130 (gp130) receptor for IL-6 and inhibits the activity of the janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway. In addition, Traf5-deficient CD4+ T cells exhibit significantly enhanced IL-6-driven differentiation of T helper 17 (Th17) cells, which exacerbates neuroinflammation in experimental autoimmune encephalomyelitis. Furthermore, TRAF5 demonstrates a similar activity to gp130 for IL-27, another cytokine of the IL-6 family. Additionally, Traf5-deficient CD4+ T cells display significantly increased IL-27-mediated differentiation of Th1 cells, which increases footpad swelling in delayed-type hypersensitivity response. Thus, TRAF5 functions as a negative regulator of gp130 in CD4+ T cells. This review aimed to explain how TRAF5 controls the differentiation of CD4+ T cells and discuss how the expression of TRAF5 in T cells and other cell types can influence the development and progression of autoimmune and inflammatory diseases.

[Understanding New Regulatory Mechanism of TCR Signal Transduction].

Signal-transducing adaptor protein-2 (STAP-2) is a unique scaffold protein that regulates several immunological signaling pathways, including LIF/LIF receptor and LPS/TLR4 signals. STAP-2 is required for Fas/FasL-dependent T cell apoptosis and SDF-1α-induced T cell migration. Conversely, STAP-2 modulates integrin-mediated T cell adhesion, suggesting that STAP-2 is essential for several negative and positive T cell functions. However, whether STAP-2 is involved in T cell-antigen receptor (TCR)-mediated T cell activation is unknown. STAP-2 deficiency was recently reported to suppress TCR-mediated T cell activation by inhibiting LCK-mediated CD3ζ and ZAP-70 activation. Using STAP-2 deficient mice, it was demonstrated that STAP-2 is required for the pathogenesis of Propionibacterium acnes-induced granuloma formation and experimental autoimmune encephalomyelitis. Here, detailed functions of STAP-2 in TCR-mediated T cell activation, and how STAP-2 affects the pathogenesis of T cell-mediated inflammation and immune diseases, are reviewed.

Lactate Dehydrogenase-Elevating Virus Infection Inhibits MOG Peptide Presentation by CD11b+CD11c+ Dendritic Cells in a Mouse Model of Multiple Sclerosis.

Infections may affect the course of autoimmune inflammatory diseases of the central nervous system (CNS), such as multiple sclerosis (MS). Infections with lactate dehydrogenase-elevating virus (LDV) protected mice from developing experimental autoimmune encephalomyelitis (EAE), a mouse counterpart of MS. Uninfected C57BL/6 mice immunized with the myelin oligodendrocyte glycoprotein peptide (MOG35-55) experienced paralysis and lost weight at a greater rate than mice who had previously been infected with LDV. LDV infection decreased the presentation of the MOG peptide by CD11b+CD11c+ dendritic cells (DC) to pathogenic T lymphocytes. When comparing non-infected mice to infected mice, the histopathological examination of the CNS showed more areas of demyelination and CD45+ and CD3+, but not Iba1+ cell infiltration. These results suggest that the protective effect of LDV infection against EAE development is mediated by a suppression of myelin antigen presentation by a specific DC subset to autoreactive T lymphocytes. Such a mechanism might contribute to the general suppressive effect of infections on autoimmune diseases known as the hygiene hypothesis.

Targeted depletion of PD-1-expressing cells induces immune tolerance through peripheral clonal deletion.

Thymic negative selection of the T cell receptor (TCR) repertoire is essential for establishing self-tolerance and acquired allograft tolerance following organ transplantation. However, it is unclear whether and how peripheral clonal deletion of alloreactive T cells induces transplantation tolerance. Here, we establish that programmed cell death protein 1 (PD-1) is a hallmark of alloreactive T cells and is associated with clonal expansion after alloantigen encounter. Moreover, we found that diphtheria toxin receptor (DTR)-mediated ablation of PD-1+ cells reshaped the TCR repertoire through peripheral clonal deletion of alloreactive T cells and promoted tolerance in mouse transplantation models. In addition, by using PD-1-specific depleting antibodies, we found that antibody-mediated depletion of PD-1+ cells prevented heart transplant rejection and the development of experimental autoimmune encephalomyelitis (EAE) in humanized PD-1 mice. Thus, these data suggest that PD-1 is an attractive target for peripheral clonal deletion and induction of immune tolerance.

Sphingolipid biosynthesis is essential for metabolic rewiring during TH17 cell differentiation.

T helper 17 (TH17) cells are implicated in autoimmune diseases, and several metabolic processes are shown to be important for their development and function. In this study, we report an essential role for sphingolipids synthesized through the de novo pathway in TH17 cell development. Deficiency of SPTLC1, a major subunit of serine palmitoyl transferase enzyme complex that catalyzes the first and rate-limiting step of de novo sphingolipid synthesis, impaired glycolysis in differentiating TH17 cells by increasing intracellular reactive oxygen species (ROS) through enhancement of nicotinamide adenine dinucleotide phosphate oxidase 2 activity. Increased ROS leads to impaired activation of mammalian target of rapamycin C1 and reduced expression of hypoxia-inducible factor 1-alpha and c-Myc-induced glycolytic genes. SPTLCI deficiency protected mice from developing experimental autoimmune encephalomyelitis and experimental T cell transfer colitis. Our results thus show a critical role for de novo sphingolipid biosynthetic pathway in shaping adaptive immune responses with implications in autoimmune diseases.

Exploring the immune-modulating properties of boswellic acid in experimental autoimmune encephalomyelitis.

Multiple sclerosis (MS) is a condition where the central nervous system loses its myelin coating due to autoimmune inflammation. The experimental autoimmune encephalomyelitis (EAE) simulates some aspects of human MS. Boswellic acids are natural compounds derived from frankincense extract, known for their anti-inflammatory properties. The purpose of this research was to investigate therapeutic potential of boswellic acids. Mice were divided into three groups: low-dose (LD), high-dose (HD), and control groups (CTRL). Following EAE induction, the mice received daily doses of boswellic acid for 25 days. Brain tissue damage, clinical symptoms, and levels of TGF-ß, IFN-γ, and IL-17 cytokines in cell cultured supernatant of lymphocytes were assessed. Gene expression of transcription factors in brain was measured using real-time PCR. The levels of brain demyelination were significantly lower in the treatment groups compared to the CTRL group. Boswellic acid reduced the severity and duration of EAE symptoms. Furthermore, boswellic acid decreased the amounts of IFN-γ and IL-17, also the expression of T-bet and ROR-γt in brain. On the contrary, it increased the levels of TGF-ß and the expression FoxP3 and GATA3. Our findings suggest that boswellic acids possess therapeutic potential for EAE by modulating the immune response and reducing inflammation.

The neurotropic schistosome vs experimental autoimmune encephalomyelitis: are there any winners?

The incidences of multiple sclerosis have risen worldwide, yet neither the trigger nor efficient treatment is known. Some research is dedicated to looking for treatment by parasites, mainly by helminths. However, little is known about the effect of helminths that infect the nervous system. Therefore, we chose the neurotropic avian schistosome Trichobilharzia regenti, which strongly promotes M2 polarization and tissue repair in the central nervous system, and we tested its effect on the course of experimental autoimmune encephalomyelitis (EAE) in mice. Surprisingly, the symptoms of EAE tended to worsen after the infection with T. regenti. The infection did not stimulate tissue repair, as indicated by the similar level of demyelination. Eosinophils heavily infiltrated the infected tissue, and the microglia number increased as well. Furthermore, splenocytes from T. regenti-infected EAE mice produced more interferon (IFN)-γ than splenocytes from EAE mice after stimulation with myelin oligodendrocyte glycoprotein. Our research indicates that the combination of increased eosinophil numbers and production of IFN-γ tends to worsen the EAE symptoms. Moreover, the data highlight the importance of considering the direct effect of the parasite on the tissue, as the migrating parasite may further tissue damage and make tissue repair even more difficult.

Identification of direct connections between the dura and the brain.

The arachnoid barrier delineates the border between the central nervous system and dura mater. Although the arachnoid barrier creates a partition, communication between the central nervous system and the dura mater is crucial for waste clearance and immune surveillance1,2. How the arachnoid barrier balances separation and communication is poorly understood. Here, using transcriptomic data, we developed transgenic mice to examine specific anatomical structures that function as routes across the arachnoid barrier. Bridging veins create discontinuities where they cross the arachnoid barrier, forming structures that we termed arachnoid cuff exit (ACE) points. The openings that ACE points create allow the exchange of fluids and molecules between the subarachnoid space and the dura, enabling the drainage of cerebrospinal fluid and limited entry of molecules from the dura to the subarachnoid space. In healthy human volunteers, magnetic resonance imaging tracers transit along bridging veins in a similar manner to access the subarachnoid space. Notably, in neuroinflammatory conditions such as experimental autoimmune encephalomyelitis, ACE points also enable cellular trafficking, representing a route for immune cells to directly enter the subarachnoid space from the dura mater. Collectively, our results indicate that ACE points are a critical part of the anatomy of neuroimmune communication in both mice and humans that link the central nervous system with the dura and its immunological diversity and waste clearance systems.

Prevention of experimental autoimmune encephalomyelitis by targeting 6-sulfo sialyl Lewis X glycans involved in lymphocyte homing.

Lymphocyte homing to peripheral lymph nodes (PLN) is critical for immune surveillance. However, autoimmune diseases such as multiple sclerosis (MS) can occur due to excessive immune responses in the PLN. Here we show that 6-sulfo sialyl Lewis X (6-sulfo sLex) glycans on high endothelial venules that function as ligands for l-selectin on lymphocytes play a critical role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. In N-acetylglucosamine-6-O-sulfotransferase (GlcNAc6ST)-1 and GlcNAc6ST-2 double-knockout mice lacking the expression of 6-sulfo sLeX glycans, the EAE symptoms and the numbers of effector Th1 and Th17 cells in the draining lymph nodes (dLN) and spinal cords (SC) were significantly reduced. To determine whether 6-sulfo sLeX could serve as a target for MS, we also examined the effects of anti-glycan monoclonal antibody (mAb) SF1 against 6-sulfo sLeX in EAE. Administration of mAb SF1 significantly reduced EAE symptoms and the numbers of antigen-specific effector T cells in the dLN and SC in association with suppression of critical genes including Il17a and Il17f that are involved in the pathogenesis of EAE. Taken together, these results suggest that 6-sulfo sLeX glycan would serve as a novel target for MS.

TCR signaling induces STAT3 phosphorylation to promote TH17 cell differentiation.

TH17 differentiation is critically controlled by "signal 3" of cytokines (IL-6/IL-23) through STAT3. However, cytokines alone induced only a moderate level of STAT3 phosphorylation. Surprisingly, TCR stimulation alone induced STAT3 phosphorylation through Lck/Fyn, and synergistically with IL-6/IL-23 induced robust and optimal STAT3 phosphorylation at Y705. Inhibition of Lck/Fyn kinase activity by Srci1 or disrupting the interaction between Lck/Fyn and STAT3 by disease-causing STAT3 mutations selectively impaired TCR stimulation, but not cytokine-induced STAT3 phosphorylation, which consequently abolished TH17 differentiation and converted them to FOXP3+ Treg cells. Srci1 administration or disrupting the interaction between Lck/Fyn and STAT3 significantly ameliorated TH17 cell-mediated EAE disease. These findings uncover an unexpected deterministic role of TCR signaling in fate determination between TH17 and Treg cells through Lck/Fyn-dependent phosphorylation of STAT3, which can be exploited to develop therapeutics selectively against TH17-related autoimmune diseases. Our study thus provides insight into how TCR signaling could integrate with cytokine signal to direct T cell differentiation.

The orphan G protein-coupled receptor 141 expressed in myeloid cells functions as an inflammation suppressor.

G protein-coupled receptors (GPCRs) regulate many cellular processes in response to various stimuli, including light, hormones, neurotransmitters, and odorants, some of which play critical roles in innate and adaptive immune responses. However, the physiological functions of many GPCRs and the involvement of them in autoimmune diseases of the central nervous system remain unclear. Here, we demonstrate that GPR141, an orphan GPCR belonging to the class A receptor family, suppresses immune responses. High GPR141 messenger RNA levels were expressed in myeloid-lineage cells, including neutrophils (CD11b + Gr1+), monocytes (CD11b + Gr1-Ly6C+ and CD11b + Gr1-Ly6C-), macrophages (F4/80+), and dendritic cells (CD11c+). Gpr141  -/- mice, which we independently generated, displayed almost no abnormalities in myeloid cell differentiation and compartmentalization in the spleen and bone marrow under steady-state conditions. However, Gpr141 deficiency exacerbated disease conditions of experimental autoimmune encephalomyelitis, an autoimmune disease model for multiple sclerosis, with increased inflammation in the spinal cord. Gpr141  -/- mice showed increased CD11b + Gr1+ neutrophils, CD11b + Gr1- monocytes, CD11c+ dendritic cells, and CD4+ T cell infiltration into the experimental autoimmune encephalomyelitis-induced spinal cord compared with littermate control mice. Lymphocytes enriched from Gpr141  -/- mice immunized with myelin oligodendrocyte glycoprotein 35-55 produced high amounts of interferon-γ, interleukin-17A, and interleukin-6 compared with those from wild-type mice. Moreover, CD11c+ dendritic cells (DCs) purified from Gpr141  -/- mice increased cytokine production of myelin oligodendrocyte glycoprotein 35-55-specific T cells. These findings suggest that GPR141 functions as a negative regulator of immune responses by controlling the functions of monocytes and dendritic cells and that targeting GPR141 may be a possible therapeutic intervention for modulating chronic inflammatory diseases.

Tolerogenic Nanovaccine for Prevention and Treatment of Autoimmune Encephalomyelitis.

Herein, a tolerogenic nanovaccine is developed and tested on an animal model of multiple sclerosis. The nanovaccine is constructed to deliver the self-antigen, myelin oligodendrocyte glycoprotein (MOG) peptide, and dexamethasone on an abatacept-modified polydopamine core nanoparticle (AbaLDPN-MOG). AbaLDPN-MOG can target dendritic cells and undergo endocytosis followed by trafficking to lysosomes. AbaLDPN-MOG blocks the interaction between CD80/CD86 and CD28 in antigen-presenting cells and T cells, leading to decreased interferon gamma secretion. The subcutaneous administration of AbaLDPN-MOG to mice yields significant biodistribution to lymph nodes and, in experimental-autoimmune encephalomyelitis (EAE) model mice, increases the integrity of the myelin basic sheath and minimizes the infiltration of immune cells. EAE mice are treated with AbaLDPN-MOG before or after injection of the autoantigen, MOG. Preimmunization of AbaLDPN-MOG before the injection of MOG completely blocks the development of clinical symptoms. Early treatment with AbaLDPN-MOG at three days after injection of MOG also completely blocks the development of symptoms. Notably, treatment of EAE symptom-developed mice with AbaLDPN-MOG significantly alleviates the symptoms, indicating that the nanovaccine has therapeutic effects. Although AbaLDPN is used for MOG peptide delivery in the EAE model, the concept of AbaLDPN can be widely applied for the prevention and alleviation of other autoimmune diseases.

NAD+ metabolism drives astrocyte proinflammatory reprogramming in central nervous system autoimmunity.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Astrocytes are the most abundant glial cells in the CNS, and their dysfunction contributes to the pathogenesis of MS and its animal model, experimental autoimmune encephalomyelitis (EAE). Recent advances highlight the pivotal role of cellular metabolism in programming immune responses. However, the underlying immunometabolic mechanisms that drive astrocyte pathogenicity remain elusive. Nicotinamide adenine dinucleotide (NAD+) is a vital coenzyme involved in cellular redox reactions and a substrate for NAD+-dependent enzymes. Cellular NAD+ levels are dynamically controlled by synthesis and degradation, and dysregulation of this balance has been associated with inflammation and disease. Here, we demonstrate that cell-autonomous generation of NAD+ via the salvage pathway regulates astrocyte immune function. Inhibition of nicotinamide phosphoribosyltransferase (NAMPT), a key enzyme in the salvage pathway, results in depletion of NAD+, inhibits oxidative phosphorylation, and limits astrocyte inflammatory potential. We identified CD38 as the main NADase up-regulated in reactive mouse and human astrocytes in models of neuroinflammation and MS. Genetic or pharmacological blockade of astrocyte CD38 activity augmented NAD+ levels, suppressed proinflammatory transcriptional reprogramming, impaired chemotactic potential to inflammatory monocytes, and ameliorated EAE. We found that CD38 activity is mediated via calcineurin/NFAT signaling in mouse and human reactive astrocytes. Thus, NAMPT-NAD+-CD38 circuitry in astrocytes controls their ability to meet their energy demands and drives the expression of proinflammatory transcriptional modules, contributing to CNS pathology in EAE and, potentially, MS. Our results identify candidate therapeutic targets in MS.

Exosomes with FOXP3 from gene-modified dendritic cells ameliorate the development of EAE by regulating the balance of Th/Treg.

Objective: To investigate the efficiency and potential mechanisms of exosomes from dendritic cells (DCs) transfected with Forkhead box protein P3 (FOXP3) in the development of experimental autoimmune encephalomyelitis (EAE). Method: Mouse bone marrow-derived immature DCs were loaded with adenovirus carrying FOXP3 gene, and exosomes were generated. Then the exosomes with FOXP3 (FOXP3-EXOs) were co-cultured with CD4+T cell in vitro to evaluate their potential on CD4+T cell proliferation and differentiation, and injected into EAE mice to assess their effects on the development of EAE. Result: FOXP3-EXOs were effective to inhibit the CD4+T cell proliferation and the production of Interferon gamma (IFN-γ), interleukin (IL)-6, and IL-17, while they promoted the production of IL-10 in vitro. Moreover, FOXP3-EXOs treatment significantly decreased the neurological scores, reduced the infiltration of inflammatory cells into the spinal cord, and decreased demyelination in comparison to saline and Con-EXOs treated EAE mice. Moreover, the FOXP3-EXOs treatment resulted in obvious increases in the levels of regulatory T (Treg) cells and IL-10, whereas levels of T helper 1 (Th1) cells, Th17 cells, IFN-γ, IL-6, and IL-17 decreased significantly in the splenocyte culture of EAE mice. Conclusion: The present study preliminarily investigated the effects and potential mechanisms of FOXP3-EXOs in EAE and revealed that the FOXP3-EXOs could inhibit the production of Th1 and Th17 cells and promote the production of Treg cells as well as ameliorate the development of EAE. The neuroprotective effects of FOXP3-EXOs on EAE are likely due to the regulation of Th/Treg balance.

Influence of Type I Interferons in Gammaherpesvirus-68 and Its Influence on EAE Enhancement.

Epstein-Barr virus (EBV) has been identified as a putative trigger of multiple sclerosis (MS). Previously, we reported that mice latently infected with murine gammaherpesvirus 68 (γHV-68), the murine homolog to EBV, and induced for experimental autoimmune encephalomyelitis (EAE), developed an enhanced disease more reminiscent of MS. These prior results showed that expression of CD40 on CD11b+CD11c+ cells in latently infected mice was required to prime the strong Th1 response driving disease as well as decreasing Treg frequencies in the periphery and CNS. Subsequent work demonstrated that transfer of B cells from latently infected mice was sufficient to enhance disease. Herein, we show that B cells from infected mice do not need type I IFN signaling to drive a strong Th1 response, yet are important in driving infiltration of the CNS by CD8+ T cells. Given the importance of type I IFNs in MS, we used IFNARko mice in order to determine if type I IFN signaling was important in the enhancement of EAE in latently infected mice. We found that while type I IFNs are important for the control of γHV-68 infection and maintenance of latency, they do not have a direct effect in the development of enhanced EAE.

NFIL3 deficiency alleviates EAE through regulating different immune cell subsets.

INTRODUCTION: The transcription factor NFIL3 exerts comprehensive effects on the immune system. Previous studies revealed that NFIL3 is related to the function and development of different immune cell subsets. Experimental autoimmune encephalomyelitis (EAE) is mediated by immune cells which results in inflammatory demyelination in the central nervous system (CNS). However, how NFIL3 affects EAE has not been thoroughly studied. OBJECTIVES: The current study aimed to investigate how NFIL3 affects EAE, especially the changes of T cells and dendritic cells as well as the crosstalk between them. METHODS: We used NFIL3-/- mice and C57BL/6J mice (wildtype) to establish MOG35-55-induced EAE. The clinical scores were recorded daily. The immune cells within and outside the CNS of EAE mice were analyzed by flow cytometry. Histology was used to evaluated the neuroinflammation and demyelination in the CNS. Besides, CD11c+ dendritic cells (DCs) were cocultured with T cells and the interplay was measured. RESULTS: At the peak of EAE, Th17 cells decreased within the CNS accompanying with lower clinical scores and milder neuroinflammation and demyelination in NFIL3 knockout EAE mice. Outside the CNS, PD-1 and ICOS on CD4+T cells increased, whereas Th2, Th9, CD8+CD103+T cells and GM-CSF+CD4+T cells decreased. Besides, the pro-inflammatory capacity of NFIL3-/- CD11c+ dendritic cells was impaired while the anti-inflammatory capacity was promoted. CONCLUSIONS: This study suggests that NFIL3 deficiency could alleviate MOG35-55-induced EAE through regulating different immune cell subsets, which is not only related with adaptive immunity and innate immunity, but also related with the cross-talk between them, especially CD4+ T cells and CD11c+ dendritic cells.

Myeloid caspase-8 restricts RIPK3-dependent proinflammatory IL-1ß production and CD4 T cell activation in autoimmune demyelination.

Caspase-8 functions at the crossroad of programmed cell death and inflammation. Here, using genetic approaches and the experimental autoimmune encephalomyelitis model of inflammatory demyelination, we identified a negative regulatory pathway for caspase-8 in infiltrated macrophages whereby it functions to restrain interleukin (IL)-1ß-driven autoimmune inflammation. Caspase-8 is partially activated in macrophages/microglia in active lesions of multiple sclerosis. Selective ablation of Casp8 in myeloid cells, but not microglia, exacerbated autoimmune demyelination. Heightened IL-1ß production by caspase-8-deficient macrophages underlies exacerbated activation of encephalitogenic T cells and production of GM-CSF and interferon-γ. Mechanistically, IL-1ß overproduction by primed caspase-8-deficient macrophages was mediated by RIPK1/RIPK3 through the engagement of NLRP3 inflammasome and was independent of cell death. When instructed by autoreactive CD4 T cells in the presence of antigen, caspase-8-deficient macrophages, but not their wild-type counterparts, released significant amount of IL-1ß that in turn acted through IL-1R to amplify T cell activation. Moreover, the worsened experimental autoimmune encephalomyelitis progression in myeloid Casp8 mutant mice was completely reversed when Ripk3 was simultaneously deleted. Together, these data reveal a functional link between T cell-driven autoimmunity and inflammatory IL-1ß that is negatively regulated by caspase-8, and suggest that dysregulation of the pathway may contribute to inflammatory autoimmune diseases, such as multiple sclerosis.